Latch-and-perf system and method

ABSTRACT

A latch and perf assembly for completion of a wellbore comprises a setting tool with an explosive charge and a wireline connector, a run-in tool installed on the setting tool, a latch installed on the run-in tool and adapted to assume a retracted state during run-in of the assembly and an expanded state when the latch arrives at a predetermined depth in the wellbore and a seal inside the latch adapted to seal against hydraulic pressure applied from surface. The assembly is adapted to be run into the wellbore attached to a wireline, and at least a predetermined part of the seal is adapted to dissolve after fracking of the wellbore.

RELATED PATENT APPLICATIONS

This patent application claims priority from the U.S. provisional Patent Application 62/690,310 filed Jun. 26, 2018.

TECHNICAL FIELD

This specification relates to a completion device and method for wellbores, and in particular, to a device and method for installing completion tools in a wellbore.

BACKGROUND

Oil well completion is the process of making a well ready for production in an oil-bearing reservoir/formation. Completion includes drilling a wellbore in the formation, preparing the bottom of the wellbore, running in a liner, cementing a casing in the wellbore around the liner, and stimulating (“fracking”) the formation.

Stimulation processes (including a fracking treatment, or a “frack”) have the function of creating an effective flow path between the reservoir and the wellbore to increase the flow of hydrocarbons through the formation.

One method to complete an oil well is called “plug-and-perf”. In this method, a liner is placed into the wellbore, and the annular space between the liner and wellbore, may be cemented through most of the length of the wellbore. The wellbore is segmented into zones that are each defined by running a fracking plug into the liner and locating the plug at a part of the wellbore corresponding to a target zone. Once a fracking plug is located in its zone, it is set with a plug setting tool, which locks the plug into the liner at a selected place in the wellbore. A perforating tool (gun) is also pumped into the wellbore and is located in the same zone as the plug. Generally, the perforation gun is run into the liner towards a target zone attached to a wireline (e.g. an E-line), which enables the use of electrical signals originating from the surface to trigger the discharge of the perforation gun. The wireline also allows two-way transmission of data, thus enabling the transmission to surface of information regarding wellbore conditions such as pressure, temperature and seismic responses. Wireline also enables the use of electrical signals to locate the plug in the correct position, to set the plug and release it, and to move the guns into the correct position before firing them.

When the plug is set, a seal is created that fluidically isolates the parts of the liner that are uphole from the plug from the parts of the liner that are downhole from the plug. After the plug is set, the gun is fired to create holes and cracks in the wall of the liner and the cemented casing at that zone, and into the formation around the wellbore. In some cases, the plug and gun (perforation tool) are deployed at the same time; the plug and gun are pumped down to the target zone from surface attached together until they reach the target zone, at which time the plug is set, and then the gun is fired. Each resulting perforation will extend from the inner bore through the liner and cement casing, and deep into the surrounding formation at that zone, creating openings between the inner bore of the wellbore and the formation. The perforation gun might then be moved uphole within the target zone in which the plug has been set, and fired again to create additional perforations at the target zone, until all the charges on the perforation gun are utilized at that target zone. The perforation gun and plug setting tool are then pulled out from the wellbore.

Fracking then occurs at the target zone by pumping fracturing (frack) fluid from the surface. The frack fluid is injected into the wellbore under pressure and passes through the created perforations in the liner and casing, and into the formation. The frack fluid flows into the perforations since the set plug prevents fluid from moving downhole of the target zone.

Fracturing fluids usually contain water, surfactants, friction reducers, proppant (sand) and other additives designed to maintain fractures (“fracks”) in the formation, which improves the flow of hydrocarbons trapped in the formation, through the fracks, and into the wellbore.

After fracking of the target zone, another plug is sent downhole on a plug setting tool and is placed in the next zone uphole from the previous target zone. The foregoing process is then repeated, until all the zones of the well have been fracked.

Since there may be well over 50 zones in a wellbore, this process can be repeated more than 50 times for each wellbore, and therefore is typically time consuming, including the steps in which plugs need to be placed and set. In addition to being time consuming, repeating the process so many times for each wellbore can be very costly, since each fracking plug needs to be removed from its respective target zone after the zone has been fracked, and the removal of each plug is also a costly operation. A plug can be removed by milling it out, which involves running a mill attached to a motor into the wellbore on coiled tubing, milling out the plug, and then using the coiled tubing to pull the mill back up to surface for future reuse.

In some more recent plug-and-perf completion operations, shaped profiles are placed at pre-selected locations in the interior of the liner, which are used to place the plugs. The plugs securely engage with the profiles by, for example, latching into the profiles. For perforating a zone, a perforation assembly including a perforation gun, a plug setting tool and a fracking plug comprising a latch, is lowered into the liner towards a target zone, using a wireline. The latch has a physical feature that is designed to correspond to the shaped profile of the target zone. The plug setting tool actuates the latch to engage with the profile of the liner at the respective target zone. Each profile in the liner thus acts as a marker that enables the setting of a perforation gun at a target zone corresponding to that profile. In this type of operation, one must mill out the plug after use.

U.S. Pat. No. 9,145,744 (Jordan) describes a completion solution that attempts to avoid milling of the plugs after fracking is completed. This patent describes using plugs that are fixed in the casing using dogs. A fracking assembly (the perforation gun, the setting tool, and the fracking plug) is then raised causing the dogs in the fracking plugs to release and allowing the entire assembly to be raised. An alternative solution described in this patent requires the operator to run back into the casing assembly with a retrieving tool to lock into the upper end of the fracking plug, which is then dragged up, forcing release of the dogs and thus enabling free movement of the plug towards surface. However, removal of the plug using force may cause damage since plugs are designed to withstand great forces applied to their uphole side (i.e., the side of the plug closest to the surface) in order to achieve their function of setting a fluid seal between the zone of interest and all parts of the wellbore downhole from that zone. High costs are incurred if the plugs need to be milled because they cannot be easily retrieved.

There is a need in the art for a more retrievable plug in completion operations that involve the setting of plugs and firing of perforation guns.

SUMMARY OF INVENTION

The perforation-gun completion device described in this specification (latch-and-pea device) is designed to minimize the above-mentioned drawbacks of prior art plug-and-pea devices. The device includes a latch for securely engaging with the liner and a seat attached to the latch for hosting a ball. The liner into which these latch-and-perf devices are lowered has identical profiles designed to engage with the devices throughout the liner, regardless of the zone. This means that the latch-and-perf devices to be deployed into a given liner can all be identical, regardless of the zone to which a given latch-and-pea device is assigned. The latch-and-pea device is secured to the liner using the latch. The latch by itself is not a seal that isolates the uphole part of the liner from the downhole part of the liner, Instead, the latch-and-pea device described in this specification uses a ball as a seal, in place of the plug of prior art systems. Once the latch is set into engagement with the liner in its target zone, a ball landed on the seat of the latch creates a seal in the liner. Fracking may occur when the seal is in place.

In one embodiment, the ball is designed to dissolve after fracking is completed. In another embodiment, the seat against which the ball seals, is designed to dissolve after fracking. In this other embodiment, the ball can be pumped downhole and away from the rest of the latching seal after the seat dissolves. Whether the ball dissolves, or the seat dissolves and the ball moves downhole, the disappearance of the ball and/or seat, allows ready access from surface to the downhole side of the latch, without any milling or otherwise removing the seal, as in previous embodiments. Specifically, the downhole side of the set latch is easily accessible from the surface, after dissolution of the ball and/or seat, through the space previously occupied by the ball and/or seat. By providing easy access to a set latch at its downhole end, the latch can be more easily retrieved without damaging the latch-and-pea device.

According to one embodiment described in this specification, a latch and pea assembly for completion of a wellbore is provided, comprising: a setting tool comprising an explosive charge and a wireline connector; a run-in tool installed on the setting tool; a latch installed on the run-in tool and adapted to assume a retracted state during run-in of the assembly and an expanded state when the latch arrives at a predetermined depth in the wellbore; and a seal adapted to seal against hydraulic pressure applied from surface to enable fracking of the wellbore, the assembly being adapted to be run into the wellbore attached to a wireline, and at least a predetermined part of the seat being adapted to dissolve after fracking of the wellbore.

This specification also describes a fracturing plug for completion of a wellbore, comprising: a latch adapted to assume a retracted state during run-in of the fracturing plug in the wellbore and an expanded state when the fracturing plug arrives at a predetermined depth in the wellbore; a seat confined inside the latch when the latch is in the retracted state, and adapted to seal the wellbore under hydraulic pressure, when the plug is in the expanded state, wherein the latch has an internal profile adapted to keep the seat inside the latch.

According to a further aspect, this specification is directed to a plug-and-pea method of stimulating production of hydrocarbons from a wellbore having a casing, comprising: running in a latch and pea assembly attached to a wireline, the assembly including a setting tool, a run-in tool installed on the setting tool, and a fracturing plug with a dissolvable seat attached to the run-in tool, with the fracturing plug in a retracted state; at a predetermined depth in the wellbore, disengaging the fracturing plug from the run-in tool causing the fracturing plug to assume an expanded state; displacing the fracturing plug downhole using fluid pumped down the liner; installing the fracturing plug at a target location in the expanded state, to pressure-isolate a target zone of the wellbore from a zone downhole the target location; retrieving the run-in tool from the wellbore; running-in at the target stage a perforating gun installed on wireline, forming a plurality of perforations in the casing along the target zone, and fracking the target zone; and then once the dissolvable seal has dissolved, retrieving the fracturing plug using a retrieving tool.

It should be noted that the terms “upper”, “uphole”, “lower”, “downhole” are relative terms used to refer to an entity located in the wellbore with respect to the surface (wellhead). For example, an “upper” feature generally refers to the feature closer to the wellhead than a corresponding “lower” feature. Position of a tool that may be referred to as “uphole” relative to a “downhole” tool, again relative to the wellhead. These terms have this meaning even in a horizontal well.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings accompanying and forming part of this specification are included to depict certain aspects of the invention. A clearer impression of the invention, and of the components and operation of devices provided with the invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings, wherein identical reference numerals designate the same components. Note that the features illustrated in the drawings are not necessarily drawn to scale.

FIG. 1 illustrates a latch-and-perf assembly lowered in a wellbore.

FIG. 2A shows a schematic view of the latch-and-perf assembly in position for installing the latching seal;

FIG. 2B shows an embodiment of the latch of the latching seal;

FIGS. 3A and 3B show the latch-and-perf assembly with the latch captured (FIG. 3A), and then with the latch released (FIG. 3B), by a retaining sleeve;

FIG. 4 shows the latch-and-perf assembly in the state it is in as it is lowered/pumped down, showing the setting tool, the run-in tool and the latching seal;

FIG. 5 shows the latch-and-pea assembly with the latching seal separated from the run-in tool after E-4 activation; and

FIGS. 6A and 6B illustrate retrieval of the latch with a retrieval tool.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrates the latch-and-pea assembly 10 according to an embodiment of the invention, and specifically illustrates the latch lowered into a wellbore 1 that is in the process of being completed. A liner 12 extends into the wellbore 1 from a wellhead 2. The liner 12 may comprise a plurality of subs (not shown) assembled together by connections (not shown). The liner is cemented in this example, as shown by casing 14.

The latch-and-perf assembly 10 described in this specification comprises a latching seal 5 (which itself comprises in an embodiment a latch 23 and a ball 21), a run-in tool 7, a wireline setting tool 9 (which may itself comprise an E-4™ setting tool) for setting the latching seal 5, and a perforating gun 40. The assembly 10 is lowered in the well toward a target location in a target zone, using a wireline 30. The wireline setting tool 9 is used to deploy the latching seal 5 in the vicinity of the target zone.

FIG. 2A also shows a locator sub 11 used to position the latching seal 5 at a predetermined depth in the liner 12. The location at which the latching seal 5 is to be set in the bore 18 provided in the liner 12, is determined by keeping track of the length of the wireline 30 deployed in the wellbore 1. Additional devices may be used that detect features in the liner in order to determine that the latch-and-perf assembly 10 has reached the target location, including a marker joint, a casing collar locator, or profiles provided in the liner at the target zone.

Once the latch-and-pea assembly 10 arrives at a predetermined depth in the wellbore in the vicinity of the target location, but uphole by a relatively short distance from the target location, a small power charge in the wireline setting tool 9 is used to free the latching seal 5 from the run-in tool 7. In some embodiments, the run-in tool 7 comprises a wireline adapter kit (not shown) provided at the downhole end of the wireline 30 to connect the wireline 30, and the wireline setting tool 9, to the latching seal 5. When the small charge carried by the wireline setting tool 9 is discharged, it creates a motion that allows the latching seal 5 to be released from the wireline 30, run-in tool 7, and wireline setting tool 9. Other means of attaching the setting tool 9 to the wireline 30 are envisaged.

Once the latching seal 5 is released from the run-in tool 7, it is pumped down a relatively short distance of 1 to 10 meters towards the locator sub 11 placed at the target location, using a small volume of fluid. The locator sub 11 is part of the liner 12 and has, in this embodiment, one or more profiles 16 with which the latching seal 5 can engage. There is a locator sub 11 for each stage of the wellbore. When the latching seal 5 latches against the profiles of the locator sub 11, the latching seal 5 is captured inside the locator sub 11 and seals up-hole portions of the the locator sub 11, from downhole portions of the locator sub 11.

FIG. 2A shows a schematic view of an embodiment of the latch-and-perf assembly 10 in a running-in configuration, as the latch-and-perf assembly 10 is lowered into the bore 18. FIG. 2A also shows the locator sub 11, which is adapted to engage with the latching seal 5 to seal the inner bore of the liner 12. As seen in FIG. 2A, the latching seal 5 comprises a ball/seal 21, an expandable latch 23 and a ball seat 32. It is to be understood that the ball/seal 21 may not necessarily have a spherical shape; any shape that provides sealing of the inner bore 18 when the seal 21 is pushed into seat 32 can be used. As indicated above, in one embodiment, the seal 21 is dissolvable. In another embodiment, the ball seat 32 is dissolvable. Other embodiments may be envisaged in which both the ball 21 and ball seat 32 are dissolvable.

As shown in FIG. 2B, in one embodiment, the expandable latch 23 has a generally tubular shape with a base 27 and a plurality of fingers 25. Each finger 25 extends from base 27 and has a free end with an outwardly extending protrusion 29 at the free end. An inwardly extending protrusion 28 is also provided at the tip of the fingers 25. The outwardly extending protrusion 29 and inwardly extending protrusion 28 are better seen on FIGS. 3A and 3B. The fingers 25 are relatively elastic in that they can assume a retracted position, when forced radially inwardly, resulting in the latching seal 5 taking on a frustoconical shape. The fingers 25 can also assume a radially expanded position, resulting in the latching seal 5 taking on a substantially cylindrical shape. With the fingers 25 in the expanded position, the inner diameter of the latching seal 5 is relatively constant along its length. With the fingers 25 in the retracted position, the inner diameter at the tip of the fingers 25 is smaller than the inner diameter of the base 27. The protrusions 29 are sized such that the external diameter at the tips of the fingers 25 is substantially equal with the external diameter of the base 27 when the fingers are retracted. The expandable latch 23 also comprises a ring seal 22, for maintaining a fluidic seal between the expandable latch 23 and the locator sub 11.

In one embodiment, the ball 21 is located inside the latching seal 5 as the latching seal 5 is run into the liner 12 toward the locator sub 11. In another embodiment, the latching seal 5 is run into the liner 12 toward the locator sub 11 without a ball 21, and a ball is later pumped into the liner 11 for landing on a seat 32 inside latching seal 5. Once the latching seal 5 has latched into the locator sub 11, the ball 21 is pumped from surface into engagement with the seat 32 of the latching seal 5. In one embodiment, the ball 21 is trapped inside the latch 23.

When fluid is pumped into bore 18 of the liner 12, the latching seal 5 comprising as indicated above the ball seat 32, the ball 21 and the latch 23, will move through the liner 12 in the downhole direction. The internal profile of the fingers 25, namely the set of inward projections 28, is designed to facilitate run-in of the seat 32. The ball 21 remains in the latch 23 until, in this embodiment, the ball 21, or in another embodiment, the seat 32 holding the ball 21, dissolves. In this embodiment, the ball seat 32 is an integral part of the latch 23. In all embodiments, when the seat 32 hosts the ball 21, and pressure is applied from surface, a seal is formed between the ball 21 and seat 32 that fluidically isolates the portion of the liner 12 that is downhole from the latching seal 5, from the portion of the liner 12 that is uphole from the latching seal 5.

In an alternative embodiment, the ball seat 32 is adapted to dissolve after fracking, the seat 32 is trapped inside the latch along with the ball 21, which may be dissolvable or non-dissolvable. When fluid is pumped into the liner 12, the entire latching seal 5 (comprising the ball seat 32, the ball 21 and the latch 23) will move through the liner 12 in the downhole direction. The ball 21 can dissolve or flow back uphole as either the ball seat 32 and/or ball 21 can dissolve.

After the latch 23 with seal 21 is pumped into the engagement with the profile (as seen for example in FIG. 5) of the locator sub 11, the latching seal 5 is set so that it isolates the current stage from the downhole stages, allowing the fracking operation to begin as soon as the wireline 30 is removed from the liner 12, and without pumping additional fluid to transport the ball to the plug as in conventional plug and perf operations.

During run-in of the latch-and-perf assembly 10, the fingers 25 are in the retracted position, with the tips of the fingers 25 forced inwardly by a retaining sleeve 33, as better seen in FIG. 3A. In this embodiment, the run-in tool 7 has a tubular body 35 and a mandrel 37. The retaining sleeve 33 maintains the latch 23 of the latching seal 5 attached to the setting tool 9. In particular, the retaining sleeve 33 retains the fingers 25 against moving radially while a shoulder 39 on the tubular body 35 retain the fingers 25 axially. The shoulder 39 is sized to engage the inward protrusion 28 of the fingers 25, Thus, as seen in the example of FIG. 3A, the upper end (uphole end) of the sleeve 33 is fixed with a pin 40 to the mandrel 37; the pin 40 goes through the wall of the tubular body 35 of the run-in tool 7. Other means of engagement may be also envisaged and used. As also seen on FIGS. 3A and 3B, a shear pin 41 keeps the sleeve in position on the body 35 of the run-in tool 7, thus also keeping the latching seal 5 attached to the run-in tool 7.

When the wireline setting tool 9 actuates by, for example, ignition of the E-4 charge carried by the setting tool 9, the highly pressurized gas that is generated, forces the inner mandrel 37 of the wireline setting tool 9 to retract in the uphole direction. As seen in FIG. 3B, this results in the shearing of the shear pins 41, and the retraction of the retaining sleeve 33, which in turn releases the fingers 25 from engagement with retaining sleeve 33 and shoulder 39. When the fingers 25 release from the retaining sleeve 33, the latch 23 is released from the run-in tool 7. Due to their elasticity, the fingers 25 of the latching seal 5 expand when the latching seal 5 is released from the run-in tool 7. As indicated above, fluid is then pumped into liner 12 from surface to move the latching seal 5 a short distance downhole to the locator sub 11.

FIG. 4 illustrates the locator sub 11 in further detail. As seen in this drawing, the locator sub 11 has an inner profile 31 sized to accommodate and retain the latch 23 of the latching seal 5. In the example of FIG. 4, the base 27 of the latch 23 (as illustrated in FIG. 3A, 3B) is retained in the portion 31 a of the locator sub, the fingers 25 are housed in the portion 31 b and when the fingers are in the expanded state, the protrusions 29 catch on the larger inner diameter of portion 31 c of the locator sub 11. When the latching seal 5 is captured in the profile 31, it is stopped from further downhole travel, causing the latching seal 5 to fluidically isolate the inner bore of parts of the locator sub 11 that are further uphole, from the inner bore of parts of the locator sub 11 that are further downhole. The location where the latching seal 5 is retained in the wellbore is referred to as the target or predetermined location 45. Other means for retaining the latching seal 5 at the target location 45 are also be envisaged.

In operation, the latch-and-perf assembly 10 is deployed in the wellbore with the latch 23, and specifically its fingers 25, in a retracted state (see FIG. 4). The wireline setting tool 9 including the charge (such as an E-4), is carried into the liner 12 attached to the wireline 30. When the latch-and-perf assembly 10 reaches a predetermined depth in proximity to, but still uphole from, the locator sub 11, the wireline setting tool 9 is actuated by an electrical signal received over wireline 30. A controlled explosion of gasses results. As a result of the force generated by the controlled explosion, pin 41 is sheared, releasing the latching seal 5 from the retaining sleeve 33. The latching seal 5 will travel downhole with the fingers 25 expanded in a radially outward direction.

In one embodiment, at the time of the outward radial movement of the fingers 25 of the latch 23 of the latch-and-perf assembly 10, the distance between the latch-and-perf assembly 10 and the target location (i.e., the profile 31 in the locator sub 11) is about three meters. The appropriate positioning of the plug-and-perf assembly 10 when the explosion by the wireline setting tool 9 is triggered, can be ensured from surface by noting the deployed length of the wireline 30. The wireline 30 is also used to send the detonation signal to the charge inside the wireline setting tool 9, when the device arrives at an appropriate depth.

Once the latching seal 5 is released from the run-in tool 7 and other parts of the latch-and-perf assembly 10, the latching seal 5 is pumped down so it lands on the locator sub 11 where it is captured in profile 31 as described above. As also described above, the ball 21 captured inside the latch 23, (or part of latch 23) sits on seat 32 and seals the internal bore 18 of the liner 12, so that the zone 70 (see FIG. 5) of the liner 12 downhole from the latching seal 5 is pressure-isolated from the zone 60 uphole from the latching seal 5.

The wireline 30 is then used to move the wireline setting tool 9 and the run-in tool 7 further uphole from the latching seal 5. The perforating gun 40 is then discharged in the sealed zone 60, for perforating the liner 12, the casing 14 around the liner 12, and the formation in the vicinity of the zone 60. Specifically, the perforating gun 40, which is run-in with the latch-and-perf assembly 10 to zone 60 that has been targeted for perforation, is discharged. The gun 40 can be moved uphole to a next location in the zone 60, and discharged again to create additional perforations through the liner, casing and in the formation at zone 60. The process can be repeated until the zone 60 is fully perforated. Thereafter, the wireline 30 with the wireline setting tool 9, spent perforating gun 40, and the run-in tool 7, are pulled out of the liner, and the zone 60 is fracked, with the latching seal 5 sealing the zone 60 against fracking fluid going downhole to for example downhole zone 70.

After fracking of zone 60 is completed, the dissolvable ball 21 and/or ball seat 32 dissolve. The latch 23 can now be easily retrieved, if the operator wishes, by running-in a retrieving tool 67, as shown in FIGS. 6A and 6B. The retrieving tool 67 can be run in using coiled tubing or jointed tubing (not shown)

FIGS. 6A and 6B show the retrieving tool 67 after being lowered downhole through the sealing latch 5 and specifically the latch 23, once the ball 21 and ball seat 32 are dissolved, or once the ball seat 32 has dissolved and the ball 21 has escaped further downhole. The retrieving tool 67 includes spring-loaded keys 65 extending outwardly from the body of the tool. The keys 65 are retracted when the tool 67 passes through the latch 23, and specifically through a space in the latch 23 vacated by the dissolved ball seat 32, and either a dissolved or removed ball 21 as seen in FIG. 6A. The keys 65 expand once they have moved past the space occupied by the ball 21 and perhaps the ball seat 32, as seen in FIG. 6B. When the keys 65 spring out, they engage the downhole side of the latch 23. Once the keys 65 have engaged with the downhole side of the latch 23, the latch 23 is then pulled up by the retrieving tool 67, allowing the latch 23 to easily disengage from profile 31 of the locator sub 11. In this way, the latch 23 is pulled out of the wellbore and can be used subsequently for a next zone to be fracked, without subjecting any part of the assembly to a significant risk of damage. Also, since the same latch 23 can be reused at different stages of the liner, every sub in the liner 12 can have identically shaped profiles 31 for engagement with the latch 23, which greatly simplifies management of the inventory of subs comprising liner 12.

In another embodiment, latching seal 5 can be used to land in an internal profile of a sliding sleeve (not shown) covering a port, (not shown) when pressure is applied uphole from latching seal 5. When it lands, latching seal 5 closes the bore 18. When the resulting force of the applied pressure crosses a threshold level, the sliding sleeve shifts to open the port, and a hydraulic frack can then be performed through the open port. This embodiment does not require perforating guns 40. 

1. A latch and perf assembly for completion of a wellbore having a liner, comprising: a setting tool comprising at least one explosive charge and a wireline connector; a run-in tool installed on the setting tool; a latch installed on the run-in tool and adapted to assume a retracted state during run-in of the assembly, and to assume an expanded state when the explosive charge is detonated, the latch attached to a seal for creating a fluidic seal against hydraulic pressure applied from surface to enable fracking of the wellbore, wherein the assembly is adapted to be run into the liner attached to a wireline, and at least a predetermined part of the seal is adapted to dissolve after fracking of the wellbore.
 2. The assembly of claim 1, wherein the latch comprises: a tubular base having a base inner diameter; and a plurality of fingers extending from the tubular base, and each having a finger tip, the fingers being adapted to enclose a frustoconical internal space with a diameter smaller than the base inner diameter when in the retracted state, and to enclose a substantially cylindrical internal space with a diameter substantially equivalent to the base inner diameter when in the expanded state.
 3. The assembly of claim 2, wherein the fingers are adapted to be forced inwardly when in the retracted state, and to autonomously expand when in the expanded state.
 4. The assembly of claim 2, wherein each finger has an outwardly extending protrusion at the tip, for enabling the latch to engage a profile provided in the liner at a predetermined depth.
 5. The assembly of claim 1, wherein the latch is enabled to engage a profile provided in the liner at a predetermined depth.
 6. The assembly of claim 1, wherein the latch is installed on the run-in tool using a retaining sleeve with an uphole end and a downhole end, the latch is joined to the run-in tool at the uphole end with a shearable pin, and the retaining sleeve is adapted to maintain the latch in the retracted state until the pin shears.
 7. The assembly of claim 6, wherein the retaining sleeve releases the latch from engagement with the run-in tool using a controlled explosion of a charge triggered by an electrical detonation signal received over the wireline.
 8. The assembly of claim 6, wherein the retaining sleeve releases the latch from engagement with the run-in tool in response to an electrical detonation signal received over the wireline.
 9. The assembly of claim 1, wherein the seal comprises a ball and a seat, and the predetermined part of the seal is the seat.
 10. The assembly of claim 1 wherein the setting tool further comprises a perforating gun, wherein the setting tool gun is adapted to be moved uphole to a location of interest upon detonation of the explosive charge, and wherein the perforating gun is adapted to be fired under control of signals transmitted over the wireline.
 11. The assembly of claim 1, wherein the latch further comprises means for engagement with a retracting tool once the predetermined part of the seal has dissolved.
 12. The assembly of claim 9, wherein the seat is made from a dissolvable material.
 13. The assembly of claim 9, wherein the ball is made from a dissolvable material and confined inside the latch when the latch is in the retracted state.
 14. The assembly of claim 13, wherein the ball can be made of various material, both degrading and non-degrading.
 15. The assembly of claim 1, wherein the liner has a plurality of profiles on its inner surface, the assembly is adapted to be run-in to a predetermined location inside the liner, the setting tool is adapted to release the latch upon detonation of the explosive charge, and the latch is adapted to be pumped into one of the plurality of profiles upon its release from the setting tool.
 16. A fracturing plug for completion of a wellbore, comprising: a latch adapted to assume a retracted state during run-in of the fracturing plug in the wellbore, and an expanded state when the fracturing plug arrives at a predetermined depth in the wellbore; a seat attached to the latch when the latch is in the retracted state, and adapted to seal the wellbore when engaged with a ball under hydraulic pressure when the latch is in the expanded state, wherein the latch has an internal profile adapted to keep the seat attached to the latch.
 17. A plug-and-perf method of stimulating production of hydrocarbons from a wellbore having a casing, comprising: running in a latch and perf assembly attached to a wireline, the assembly including a setting tool, a run-in tool installed on the setting tool, and a fracturing plug with a dissolvable seat attached to the run-in tool; at a predetermined depth in the wellbore, disengaging the fracturing plug from the run-in tool and causing the fracturing plug to switch from a retracted state to an expanded state; displacing the fracturing plug downhole using fluid pumped down the liner; installing the fracturing plug at a target zone of the wellbore; pressure isolating the target zone from a zone downhole from the target zone by pumping a seal into engagement with the seat; running in at the target zone a perforating gun; using the fracking gun to form a plurality of perforations in the casing along the target zone; and, fracking the target zone.
 18. The method of claim 17, wherein the predetermined depth is about 3 m uphole from the target zone.
 19. The method of claim 17, wherein the latch and pea assembly is attached to the wireline using a wireline adapter kit.
 20. The method of claim 17, further comprising transmission of an electrical detonating signal to the setting tool over the wireline for triggering a small detonation that disengages the fracturing plug from the run-in tool.
 21. The method of claim 18, wherein installing the fracturing plug at the target zone is achieved by fitting the fracking plug against an indentation provided in a locator sub provided at the target zone.
 22. The method of claim 17, further comprising retrieving the fracturing plug using a retrieving tool.
 23. The method of claim 17, wherein the retrieving tool has spring-loaded keys, extending outwardly from the body of the retrieving tool.
 24. The method of claim 17, wherein the seal is a dissolvable ball adapted to seal the target zone from a zone downhole from the target zone until the ball has dissolved.
 25. The assembly of claim 1 wherein the latch comprises a dissolvable material.
 26. The assembly of claim 1 wherein the latch is adapted to engage a profile of a plurality of profiles provided in a liner installed in the wellbore.
 27. The assembly of claim 26 wherein the latch is adapted to open a port in the liner upon creation of a seal at the latch, and upon application of a threshold pressure from surface.
 28. The assembly of claim 27 wherein the port is adapted to be used for hydraulic fracturing upon being opened. 